The invention relates to a machine tool consisting of at least one tool spindle which can be moved and positioned in at least one working plane by a movement system.
The above-mentioned machine tools are well known in the engineering industry. They are often used in transfer lines, assembly centres, machining centres and the like. They are characterised by a high degree of flexibility and moveability and are capable of carrying not only one but a plurality of tool spindles simultaneously, the tool spindles also driving various tools for example. It is also known to connect intelligent tool replacement systems or tool magazines to the machine tools in order to increase the efficiency of such machine tools.
The tool spindle is to be positioned in relation to the tool in at least one plane, the working plane, by a movement system. It is also quite possible to position the machine tool in relation to further axes. There are, for example, so-called stages with X and Y movements in which a first carrier has a second carrier which can be moved on the first carrier and therefore provides a movable movement system for the tool spindle at least in one plane. These arrangements are also known as xe2x80x9cCartesian machinesxe2x80x9d, in other words the relevant axes of movement are arranged at right angles to one another.
The disadvantage with this development is that the first carrier has to be designed so as to be very large as it has to carry and bear not only the weight of the tool spindle and the working force to be exerted but must also in addition bear the weight of the second carrier. On the basis of this principle, this leads to relatively large and heavy machine tools.
On the basis of this known principle, large drive units have to be provided in order to accelerate the high masses in a tolerable amount of time, so the machining times cannot increase too greatly. Therefore, not only the bulky design of such a machine tool but also the more complex drives required lead to increased costs in such machine tools.
The object of the invention therefore is to provide a machine tool, as described at the start, which is simple and economical in terms of production and simultaneously permits a high machining speed.
This object is achieved with a machine tool, as described at the start, in which the movement system comprises at least two guide rods which are connected to one another in an articulated manner by a guide rod joint, each of said guide rods having a free end, said free ends of the guide rods being moveable in opposite relative directions towards and apart from one another and/or in the same direction as one another.
The constructional assembly of parts of the movement system on top of one another is avoided as a result of this concept of the movement system. The two guide rods, which are connected to one another by a guide rod joint, effect a movement in the working plane of the tool spindle. Depending on whether the guide rods move towards one another or apart from one another, the work spindle moves in a first dimension. If the two guide rods move in the same direction, a second dimension results which is arranged at right angles to the first dimension and therefore defines a substantially freely determinable working face which can be covered by the tool spindle. A relative movement of the two guide rods towards one another is also sufficient for the first dimension, in other words, one guide rod can, for example, also remain stationary. A similar effect can be achieved through appropriate selection of the guide rod lengths and the arrangement of the guide rod joint on the guide rods.
The tower-like stage arrangement with X and Y movements of the machine tools results from the proposal according to the invention and a considerably simpler machine tool is produced with considerably lower masses as these no longer have to mutually support one another. This means that not only a smaller number of components is possiblexe2x80x94only two guide rods which are connected in an articulated manner and which can be moved towards one another are substantially required for this purpose, and also, owing to the lower masses, smaller and therefore more favourable drives are required in order to achieve the same accelerations according to Newton""s law of motion. The tool spindle is therefore positioned with smaller drives in the same amount of time, so the cost of the drive for the movement system is lower than that of the known stage arrangements with X and Y movements whilst retaining the same speed.
The invention does not prevent more than just two guide rods being provided according to the invention. The same also applies to the number of guide rod joints. It is possible, for example, to use the above-mentioned principle in the context of scissor kinematics and the like, for example.
In a preferred development of the invention, it is provided that the guide rods rest on the same plane. As an alternative to this, it is of course also possible to mount the guide rods at different levels in order to achieve specific geometric relationships. Similarly, according to the invention, it is also conceivable that the arrangement is mounted not only on one planexe2x80x94it is also possible in the same manner that the guide rods are arranged so as to be suspended on a plane or supported on a plane extending substantially vertically. Appropriate guides are provided for the guide rods for this purpose.
Furthermore, it is favourable if the guide rod is mounted in an articulated manner on a guide rod base by a base joint. In the process, the guide rod base forms for example the slide on a track for movement of the guide rod. In order to achieve appropriate stability of the machine tool, it is obviously provided that the guide rod base can be mounted on a plurality of tracks which run in parallel. As an alternative to a guide rod base, and also acting similarly thereto, the guide rod in the lower region rests on a rotatable element, for example a roller or the like, the axis of rotation of this roller is then at the same time also being the axis of rotation of the xe2x80x9cbase jointxe2x80x9d.
A ball spindle, a linear drive, a chain or belt drive, or a rack and pinion arrangement, for example, is provided as a drive for the guide rod or the guide rod base. The drive effects the movement of the guide rods in the same direction or in opposite directions in order to move either the tool spindle in the direction of the track (when moving with one another) or at right angles thereto (when moving in opposite directions to one another). In this case it does not matter whether the above-described drives act directly on the guide rod base or act on parts of the guide rod which are then optionally movably mounted.
The design of the drives is of course very important as the tool spindle is ultimately positioned relative to the workpiece to be machined by precise positioning of the drives. Known control means are used here, the respective geometric relationships being taken into account for positioning of the tool spindle.
In the conventional manner, the drive control is appropriately provided with data by the machine control device in order to execute appropriate positioning. The entire process preferably takes place in this case using microprocessor-aided control devices and is, for example, appropriately carried out in a comprehensively integrated manner in more complex transfer lines or machining centres.
In a preferred development of the invention, it is provided that the axis of rotation of the tool spindle can be oriented or adjusted so as to be parallel, at right angles or at any angle to the axis of rotation of the guide rod joint. In a first embodiment the machine tool is designed as a three-axis machine. The tool spindle can be moved at right angles to the working plane predetermined by the guide rod so the axis of rotation of the tool spindle is parallel to the joint axis of the guide rod joint. It is also possible, however, to select an arrangement at right angles thereto in order to achieve a forward movement of the tool spindle in axis direction, for example, as a result of the movement of the guide rods. Greater flexibility is achieved if the spindle can be moved relative to the movement system, for example is rotatably mounted about a fourth axis. As a result, it is also possible to carry out relatively complex operations using the four-axis machine thus produced.
It is also proposed that the entire movement system is arranged on a slide which can be moved separately. The guide rods are movably mounted on the slide, for example by the already described guide rod bases. As a result of such a development, the working face can be considerably expanded parallel to the direction of movement of the slide and a larger working space can be provided for the work spindle as a result. At the same time it is possible to implement still quicker positioning owing to superimposition of the movement of the slide and of the movement of the guide rod on the slide.
In a preferred development it is also provided that the guide rods are of the same length. The length of a guide rod is determined in this case by the spacing of the relevant axes. In this case, the spacing between the joint axis (guide rod joint) and the base axis (base joint) is to be considered. With such geometry, the guide rod joint is always located between the two guide rod bases or the respective base joints. The work spindle is then also preferably arranged in the vicinity of the guide rod joint in order to exploit these geometric properties for positioning of the tool spindle.
Alternatively, however, it is also possible that the guide rods are of different lengths in the context of the invention and the longer first guide rod carries the tool spindle. As a result it is possible, with appropriate control and appropriate dimensioning of the relevant guide rod lengths, to cover relatively complicated machining curves with the work spindle.
It is also proposed according to the invention in this case that the guide rod joint on the first guide rod is located between the drive spindle and the guide rod base. As an alternative to this, it is also quite possible for the drive spindle to be located between guide rod joint and guide rod base.
In a preferred development according to the invention, it is provided that the guide rod joint is located in the middle of the first guide rod. This means that the distance between the joint axis and the base axis of the base joint of the first guide rod is the same as the distance between the joint axis and the axis of rotation of the drive spindle. This of course assumes that the drive spindle is oriented or can be oriented parallel to the joint axis.
Relationships which are relatively simple and favourable for the operation are also created in particular if the length of the second short guide rod corresponds to the length of the portion of guide rod of the first guide rod from guide rod joint to tool spindle. As a result, viewed from the perspective of the guide rod joint, the distance to the base joint of the shorter guide rod is the same as the distance to the work spindle. These two parts therefore form an isosceles triangle. Three parts of equal length, namely the first shorter guide rod and the two parts on the longer first guide rod result in particular if the guide rod joint is now arranged in the middle of the first larger guide rod. As a result, the axis of rotation of the work spindle is always located above the base axis of the base joint of the shorter second guide rod. Owing to this simple geometric relationship, a right-angled work space is described in a simple manner for the work spindle as this connecting line follows at right angles to the track.
As machining operations are to be carried out on the workpiece using the machine tool, it is favourably proposed that the machine tool is separated from the machining space by panelling, the panelling being penetrated by the tool spindle. As a result, the situation where swarf removed by the workpiece located in the machining space finds its way into the region of the machine tool and blocks, soils or impairs in some other way the sensitive joints, drives, etc, is avoided. The panelling consists in this case of a movable plate-like curtain consisting of a plurality of parts, wherein the parts can be moved telescopically one on top of the other in such a way that closed panelling results.
In order to secure the panelling it is provided that it is connected at least at a base joint and/or at the tool sleeve to the movement system. In this case it is favourable if the previously described relationship of the short guide rod to the two parts of the long guide rod prevails, so the position of the axis of rotation of the tool spindle in relation to the base axis of the base joint is already fixed in the space or is still undetermined in one dimension only and in this case in particular, for example, the panelling is already guided at two points by an appropriate guide and therefore the danger of vibrations, fluttering or other instabilities in the panelling during operation, in particular in the event of large accelerations, is considerably reduced. The panelling is preferably fixed on two or even three fixing points of the movement system at least with respect to one of the remaining degrees of freedom. It is favourable in this case, when using both base joints, that this connecting line is located at right angles to the line connecting the base joint of the shorter guide rod to the axis of rotation of the tool spindle as the panelling can be connected and secured to the movement system in a simple manner as a result. Consequently, reliable protection of the machine tool against swarf produced in the machining space is achieved in a simple manner, which protection is accompanied by simple control of the position of the tool spindle.
In a preferred development of the invention, it is provided that the first long guide rod is designed as a parallelogram-like double guide rod and each part of the double guide rod carries a tool spindle. The guide rod base is accordingly designed so as to be correspondingly elongated in order to receive a second base joint for the second part of the double guide rod. At the top end of the guide rod the parallelogram is closed by a further transverse guide rod, the tool spindle preferably being positioned in relation to the respective parts of the double guide rod to facilitate control. It can however be extremely advantageous for suitable machine tools to deviate from this symmetry. Such a development of the invention results in higher levels of performance in particular with equidistant machining operations which are determined by the length of the transverse guide rod. Furthermore, there is also the possibility of changing the tool on the first tool spindle while machining is taking place at the second tool spindle. For this purpose the tool spindle, which is arranged on a tool sleeve for example, is withdrawn completely, a suitable robot then changing the tool. Owing to the parallel sequence of functionsxe2x80x94machining on the one hand and changing of the tool on the other handxe2x80x94machining times and set-up times are also reduced. A greater degree of effectiveness of such a machine tool results.
In order to make better use of the track, it is proposed that two or more movement systems are arranged on a common track. It does not matter in this case whether the respective movement systems are designed so as to be identical or different. This can be determined by the corresponding intended use. It is also possible, for example, that the track with the movement systems is provided parallel to the machining line and a machining space is not permanently associated with a machine tool but instead a flexible association is obtained. When optimising operating sequences, this can provide considerable simplification and increased efficiency. It is also proposed that two movement systems which are arranged symmetrically to one another are used on one track. In this case, for example, the guide rod base, which is arranged between the two movement systems, can serve both adjacent movement systems. Such a development can, for example, be advantageous with symmetrically designed workpieces as common positioning of the two tool spindles is achieved by a common drive and as a result a plurality of steps can be carried out simultaneously which can also lead to a considerable saving in time.
As a result of the proposal according to the invention, a machine tool which is clearly lighter in mass than the known Cartesian machine tools is achieved. This lower mass means that higher machining speeds and positioning speeds can be implemented with the machine tools according to the invention. It is also possible to accelerate the lower masses more with the same drives or drive forces. However, it is not only the advantages of such a machine tool during operation which are prominent. Such a machine tool according to the invention is also easy to produce as simple geometric elements, namely the guide rods, are to be formed, and it is also possible in the case of the latter to use modern materials such as fibre reinforced plastics materials, in particular glass fibre or carbon fibre reinforced plastics materials, in the region of the guide rods or the joints. An additional reduction in weight is achieved as a result. The above-mentioned materials can of course be used, not only for the joints but also for the guide rods.